Since the advent of synthetic yarns, it has been recognized that they do not have the aesthetic qualities existent in natural fibers such as cotton and wool. Although numerous attempts have been made, these natural fiber qualities such as soft texture and sheen have been difficult to duplicate in synthetics. Conversely, synthetics offer better processing and uniformity qualities than natural fibers. The characteristics which permit better hand (feel) and appearance--nonconformity of cross-section and length, to name two--make handling the natural fibers difficult.
Attempts to manufacture continuous filament synthetic yarns with natural fiber characteristics have followed numerous routes. Continuous filaments have been cut (U.S. Pat. No. 2,077,079), abraded (U.S. Pat. No. 2,255,755), and overdrawn (U.S. Pat. No. 3,137,991) to break or sever the filaments. The broken or severed filaments were to jut out from the remaining bundle to trap air for a "natural" feel to the touch.
Overfeeding one group of continuous filaments with respect to a second group and combining the two groups in a fixed relationship has been another means of attempting to duplicate the feel of natural fiber, the overfed filaments tending to flare out from the overall bundle. Various methods of combining and relatively fixing the two groups have been tried. Yarns have been plied and cabled together wherein the yarns differentially shrank when heated (U.S. Pat. No. 2,575,753). Ends of continuous filaments have been combined through falsetwisting apparatus (U.S. Pat. Nos. 3,217,482 and 3,763,640). Air or fluid entanglement has produced varying effect yarns (e.g. U.S. Pat. Nos. 3,167,847, 3,811,263, and 4,051,660).
Continuous filament synthetic yarns and natural fibers have also been combined to attempt to obtain the better characteristics of each type. U.S. Pat. No. 2,854,812 combines wool, cotton, or "man-made" fibers in a "spun" yarn with a stretchable nylon through a ringtwisting apparatus which wraps the two together. U.S. Pat. No. 2,990,673 discloses drafting and twisting fibers of a small amount of twist around a core material comprising continuous filaments with little or no twist. Similar disclosures are found in U.S. Pat. Nos. 3,153,316; 3,259,939; 3,845,611 and 3,835,638. To date, however, there has been no successful--i.e. commercially viable--blending of the better attributes of spun staple fibers and continuous filament yarns.